1. Field of the Invention
The present invention relates to an electric shaver and more particularly to an inner cutter unit and an outer cutter unit provided in an upper portion of a rotary type or reciprocating type electric shaver.
2. Prior Art
In rotary type or reciprocating type electric shavers, a shaver head frame is disposed on the upper portion of a main body case of a shaver. In the shaver head frame, inner and outer cutter units are detachably installed; and the main body case includes, in addition to other components, a driving source (motor), a driving mechanism, a power supply section and an operating switch.
The inner cutter unit generally comprises a plurality of inner cutter blades formed in an upright posture in the circumferential direction on an inner cutter base that is made of a synthetic resin. The inner cutter unit is installed in the shaver head frame with its inner cutter base engaged with a driving shaft of a driving mechanism, the driving shaft extending from the main body case of the shaver.
On the other hand, the outer cutter of the outer cutter unit is integrally supported in an outer cutter frame, and the outer cutter unit is installed in the shaver head frame so as to cover the inner cutter unit.
Some shavers have only one set of inner and outer cuter cutter units, and other shavers include a plurality of (three, for instance) sets of inner and outer cutter units.
The outer cutter is formed in a mesh configuration in which hair entry openings through which hair is introduced are formed by partition ribs that form outer cutter blades. The inner cutter blades have blade surfaces and the outer cutter blades have blade surfaces, and these blade surfaces face each other.
The inner cutter blades are rotationally driven (in a rotary shaver) or caused to make a reciprocating motion (in a reciprocating shaver) together with the inner cutter base. Hair that is introduced into the hair entry openings is cut when the blade surfaces of the inner cutter blades rotate (in a rotary shaver) or make a reciprocating motion (in a reciprocating shaver) while sliding (in the direction of arrow in FIG. 3) against the blade surfaces of the outer cutter.
Some shavers include only one set of inner cutter unit and outer cutter, and other shavers involve a plurality of (three, for instance) sets of inner and outer cutter units.
FIG. 3 shows a relationship between an outer cutter 51 and one of the inner cutter blades 52 of an electric rotary shaver of prior art.
In this shaver, the outside surface portions 53 of the ribs 58 (two ribs 58 are shown in FIG. 3) that define the hair entry openings 57 in the outer cutter 51 are coated with a synthetic resin 54 such as Teflon, etc. This coating is made in order to provide a smooth contact of the shaver with the skin and in order to provide a particular design effect. In some shavers, each of the ribs 58 (see the right side rib 58) is formed with an inside surface recess 55, and this recess 55 is filled with a synthetic resin 54 in order to provide smooth sliding contact between the outer cutter 51 and the inner cutter blade 52.
However, the prior art outer cutter 51 shown in FIG. 3 has several problems.
Firstly, if the adhesive force of the synthetic resin 54 that covers the outside surface portions 53 or is filled in the inside surface recess 55 is not securely maintained, the resin 54 is peeled off during the use of the shaver. If, for instance, the resin 54 on the outside surface portions 53 is peeled off, the contact of the shaver with the skin becomes poor, and the design characteristics are also deteriorated. If the resin 54 in the inside surface recess 55 is detached, the friction with the blade surface 56 of the inner cutter blade 52 increases, and the rotational efficiency (oscillation efficiency in the case of a reciprocating shaver) can easily decrease.
Secondly, for the resin 54 that is applied as a coating on the outside surface portions 53 of the outer cutter 51, there is nothing to serve as a reference for the thickness of such a resin 54. As a result, even thickness of the resin 54 is not obtainable for all the outside surface portions 53 of the outer cutter 51.